This invention relates to a process for cleaning a gas turbine's fuel nozzles while the turbine is in operation.
Gas turbines, typically, may contain up to fourteen fuel gas nozzles being fed by a common gas header. The exit gas temperature at the exhaust of the gas turbine is usually monitored to determine the temperature spread of all the nozzles, that is, the temperature difference between the nozzle with the lowest temperature and the nozzle with the highest temperature. During operation of a gas turbine, it is important to minimize the exhaust temperature spread because an excessive temperature spread, for example more than 100 degrees Fahrenheit, creates thermal cycling which can lead to breakdown of turbine blades and shutdown of the turbine.
It has been found that plugging of fuel nozzles by liquids and particulate matter in the gaseous fuel can increase the temperature spread great enough to shut down a gas turbine operation. "Dirty" fuel containing, for example, hydrocarbon liquids, salts or sulfur contaminants, typically, can be fed into a gas turbine from, for example, underground or off-shore gas wells.
Heretofore, there has not been an adequate process for cleaning gas turbine gaseous fuel nozzles while the gas turbine is in operation. In the past, gas turbines had to be shutdown for several hours to allow cooling and subsequent removal and cleaning or replacement of fuel nozzles. These shutdowns cost users of gas turbines several thousand dollars per occurrence.
It is desired to provide a process for cleaning an operating gas turbine's gaseous fuel system to clean dirty gas firing nozzles reducing the differential in temperature between the highest and lowest monitored nozzle or turbine exhaust temperatures within a short period of time to avoid having to shutdown the unit to replace and/or clean the nozzles.